The present invention relates to an ellipsometer for studying optical characteristics or film thickness of a sample by detecting a change in polarization of light, which has been plane-polarized before reflected by a surface of the sample.
The ellipsometer is an instrument or apparatus that studies optical characteristics or film thickness of a sample by basically causing plane-polarized light to be reflected at a surface of the sample and then measuring resultant elliptically-polarized light produced by the reflection.
There is a type of the ellipsometer, which causes plane-polarized light to be successively reflected by an objective sample to be measured and a reference sample as a criterion for comparison. Such ellipsometer is designed such that influences to the polarization by the respective reflections at the objective and reference sample surfaces are cancelled out when the optical characteristics of the surface of the objective sample are coincident with those of the reference sample. Since the ellipsometer detects difference in optical characteristics between the reference and objective sample surfaces, it has a relatively high sensitivity.
In the ellipsometer using the reference sample and the objective sample, both samples should be accurately positioned. In other words, both of the reference sample and the objective sample should be placed at appropriate positions and in appropriate orientations.
The most general manner for producing plane-polarized light having a specific plane of polarization is to cause nonpolarized light to pass through a polarizer, which allows light having a specific plane of polarization to transmit therethrough. In practice, the ellipsometer generally employ the plane-polarized light produced in this manner.
However, such ellipsometer has extremely low utilization ratio of light. More specifically, the ratio of light components transmitting through the polarizer to those incident upon the polarizer is very low. The low utilization ratio of light is a main reason why the ellipsometer enabling highly accurate measurement has not been attained.
An object of the present invention is to provide an ellipsometer capable of placing a reference sample and an objective sample to be measured at appropriate positions and in appropriate orientations, and also provide a sample positioning mechanism for use in appropriate positioning.
Another object of the present invention is to provide an ellipsometer efficiently utilizing light, and also provide a polarization angular adjusting mechanism for use in the apparatus.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.